Conventionally known resist materials are generally polymeric materials capable of forming amorphous thin film. For example, a solution of polyhydroxystyrene derivative is applied on a substrate to form a thin resist film, which is then irradiated with ultraviolet rays, far ultraviolet rays, electron beams, X-rays, etc., to form line patterns having a line width of about 0.08 μm.
The known polymeric resist compounds generally have a molecular weight as large as about 10,000 to 100,000 and a broad molecular weight distribution, and their polymer chains are entangled with each other. Therefore, in a lithographic fine process using such polymeric resist compounds, the surface of the fine patterns is roughened, thereby making it difficult to control the dimension of patterns, reducing the product yield, and impairing the transistor characteristics. Therefore, it has been difficult to form patterns having a line width of 0.06 μm or less in the conventional lithographic techniques using the known polymeric resist materials. To produce finer patterns, there have been proposed various low-molecular resist materials with narrow molecular weight distributions.
Known non-polymeric resist materials include, for example, (1) positive- or negative-type resists derived from fullerenes (Patent Documents 1 to 5), (2) positive- or negative-type resists derived from calixarenes (Patent Documents 6 to 8), (3) positive-type resists derived from starburst-type compounds (Patent Documents 9 to 11), (4) positive-type resists derived from dendrimers (Non-Patent Document 1), (5) positive-type resists derived from dendrimer/calixarene (Patent Documents 12 to 13), (6) positive-type resists derived from highly branched starburst-type compounds, (7) positive-type resists derived from ester linkage-containing starburst-type compounds mainly constituted by a trimesic acid structure (Patent Document 14), (8) positive-type resists derived from calix resorcinarenes (Patent Document 15), (9) positive-type resists derived from nitrogen-containing branched polyphenols (Patent Document 16), and (10) positive-type resists derived from compounds having a spiroindane structure or spirobichroman structure (Patent Document 17).
The resist materials (1) are good in the etching resistance but not practical in the coating properties and sensitivity. The resist materials (2) are excellent in the etching resistance, but fail to form satisfactory patterns because of a poor solubility in a developing solution. The resist materials (3) have a low heat resistance, and therefore, may cause the distortion of patterned images during the heat treatment after exposure to light. The resist materials (4) are less practicable because a complicated production process is required and the distortion of patterned images due to their low heat resistance occurs during the heat treatment after exposure to light. The resist materials (5) are less practicable because a complicated production process is required and the raw materials are expensive. The resist materials (6) are less practicable because a complicated production process is required, the raw materials are expensive, and the use of metal catalysts, which are detrimental to the production of semiconductors, is needed. The resist materials (7) are less practicable because the distortion of patterned images due to their low heat resistance is likely to occur during the heat treatment after exposure to light and the adhesion to substrates is poor. The resist materials (8) are less practicable because they are less amorphous and the use of metal catalysts, which are detrimental to the production of semiconductors, is needed to require complicated operations for the purification. The resist materials (9) are less practicable because of their poor resolution. The resist materials (10) are less practicable because the distortion of patterned images due to their low heat resistance is likely to occur during the heat treatment after exposure to light and the adhesion to substrates is poor.
Also disclosed is the addition of a low-molecular compound to a photosensitive resin composition. There have been discloses a photosensitive resin composition which contains a photosensitive compound having a hydrophobic group selected from hydrocarbon groups and heterocyclic groups, a linking group, and a hydrophilic group protected by a protecting group which can be cleaved by the exposure to light (Patent Document 18), a resist composition containing a low-molecular dissolution inhibitor having a non-conjugated structure of two or more triphenylmethane radicals in addition to a group decomposable by an acid (Patent Document 19), and a resist resion composition containing a photosensitive compound having a fluorene structure (Patent Document 20). However, a composition containing the compound of the present invention, which will be described below, as a main component is not hitherto disclosed. Since any of the proposed resist compositions contain a resin, the patterns obtained have a large line edge roughness to make the compositions insufficient for use.
The use of known resist compounds as the main component involves any of the problems of having a low resolution due to a small solution contrast, having a poor film-forming property due to a high crystallizability, failing to exhibit a heat resistance withstanding the semiconductor process, being hardly soluble to safety solvents such as propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, butyl acetate, methyl 3-methoxypropionate and ethyl propionate which are acceptable to the production of semiconductor, and having a poor adhesion to substrate. Therefore, the sole use of known resist compounds has been difficult. For example, a resist composition containing a compound having a non-conjugated structure of two or more triphenylmethane radicals in addition to a group decomposable by an acid (Patent Document 21) and a resist composition containing various types of polyphenols as the main component (Patent Document 22) are unsatisfactory because of their low resolution.
The inventors have proposed, as a non-polymeric resist material for solving the above problems, a resist compound and resist composition mainly composed of a polyphenol compound which is produced by the condensation of phenol with an aromatic ketone or aromatic aldehyde (Patent Document 23). Using the resist compound and resist composition, fine patterns of a line width of 0.06 μm or less can be formed. However, it has been found that the solution contrast, heat resistance, etc. should be improved for producing still finer patterns.    [Patent Document 1] JP 7-134413A    [Patent Document 2] JP 9-211862A    [Patent Document 3] JP 10-282649A    [Patent Document 4] JP 11-143074A    [Patent Document 5] JP 11-258796A    [Patent Document 6] JP 11-72916A    [Patent Document 7] JP 11-322656A    [Patent Document 8] JP 9-236919A    [Patent Document 9] JP 2000-305270A    [Patent Document 10] JP 2002-99088A    [Patent Document 11] JP 2002-99089A    [Patent Document 12] JP 2002-49152A    [Patent Document 13] JP 2003-183227A    [Patent Document 14] JP 2002-328466A    [Patent Document 15] JP 2004-191913A    [Patent Document 16] JP 2004-341482A    [Patent Document 17] JP 2005-91909A    [Patent Document 18] JP 2002-363123A    [Patent Document 19] JP 2001-312055A    [Patent Document 20] JP 2004-137262A    [Patent Document 21] WO 2005/081062    [Patent Document 22] JP 2005-309421A    [Patent Document 23] WO2005/029189    [Non-Patent Document 1] Proceedings of SPIE vol. 3999 (2000) P1202-1206